Polytype electroconductive powders

ABSTRACT

The disclosure relates broadly to a new class or type of electroconductive powders (ECP), designated as Polytype ECP (PECP), comprising intimate mixtures of several types of ECP powders. PECP mixtures possess a lower electrical resistivity, or a higher electroconductivity, than would be expected from the weighted average of the component ECP powders. PECP are multi-component and may contain many different types of ECP. ECP components of the PECP can be selected from at least one member of the group consisting of crystallites of tin oxide containing antimony in solid solution, crystallites of antimony-containing tin oxide with uniformly distributed amorphous silica, two dimensional networks of crystallites of antimony-containing tin oxide in a unique association with amorphous silica or silica-containing material, filler materials, metal coated powders, conventional ECP materials such as carbon, aluminum powder, among others.

This is a continuation of application Ser. No. 08/100,875 filed Jul. 30,1993, now abandoned.

FIELD OF THE INVENTION

The present invention relates to a new class of electroconductivepowders (hereinafter referred to as "ECP"). When the ECPs of theinvention are incorporated in coatings, films, among many othermaterials, the ECPs form an interconnecting electroconductive network.

BACKGROUND OF THE INVENTION

Electroconductive powders in general, and those comprisingantimony-containing tin oxide and using such powders for impartingelectroconductive properties to a wide variety of surfaces are knowngenerally to the art.

National SAMPE Technical Conference 17,410-419, 1985 describes a powderconsisting of conductive Sb-doped SnO2 which is used in a paint toproduce a transparent conductive film. Journal of Materials Science,21,2731-2734, 1986 describes Sb-doped SnO2 films on glass substrates.Japanese Patent No. SHO 63[1988]20342 discloses a method ofmanufacturing fine electroconductive mica particles by coating them witha tin oxide/antimony oxide mixture. Japanese Patent 63(1989)285119discloses electroconductive powders comprising flaked particles, such asmica or kaolinite which are coated with TiO2 and SnO2 containing 0.1 to25 wt % Sb. U.S. Pat. Nos. 4,373,013 and 4,452,830 disclose preparing anelectroconductive powder having a structure comprising titanium oxideparticles as nuclei with a coating of antimony-containing tin oxide onthe surface of the titanium oxide particles. European Patent ApplicationPublication No. 0 359 569 (which corresponds to U.S. patent applicationSer. No. 07/386,765, now allowed), discloses electroconductivecompositions comprising particles having a thin surface layer ofamorphous silica or silica-containing material, said material having athin surface coating layer which comprises a network ofantimony-containing tin oxide crystallites. U.S. Pat. No. 5,024,826discloses an amorphous silica material in the form of hollow shellswhich are obtained by dissolving the original particle on which thesilica was deposited. U.S. patent application Ser. No. 07/905,980 filedon Jun. 29, 1992 discloses an electroconductive powder which is in theform of agglomerates comprising fine crystallites of antimony-containingtin oxide uniformly distributed with amorphous silica. Further, U.S.patent application Ser. No. 07/906,076 filed on Jun. 29, 1992 disclosesan electroconductive powder which is in the form of an electroconductingnetwork of antimony-containing tin oxide crystallites and silica upon asubstrate particle. U.S. Pat. No. 5,192,613 discloses anelectroconductive film, which can contain two types of electroconductivematerials described in European Patent Application Publication No. 0 359569 (corresponding to U.S. patent application Ser. No. 07/386,765), thatare added separately to a polymeric binder prior to casting anelectroconductive coating for making an electrographic recordingelement.

The disclosure of each of the above-identified documents, patentapplications and patents is hereby incorporated by reference.

SUMMARY OF THE INVENTION

The present invention relates broadly to a new class or type ofelectroconductive powders (ECP), designated as Polytype ECP (hereinafterreferred to as "PECP"), comprising intimate mixtures of several types ofECP powders. PECP are multi-component and may contain many differenttypes of ECP. Binary or ternary mixtures are normally preferred. In anembodiment the electroconductive property derives fromantimony-containing tin oxide crystallites. PECP mixtures possess alower electrical resistivity, or a higher electroconductivity, thanwould be expected from the weighted average of the component ECPpowders.

ECP components of the PECP can be selected from at least one member ofthe group consisting of crystallites of tin oxide containing antimony insolid solution, crystallites of antimony-containing tin oxide withuniformly distributed amorphous silica, and two dimensional networks ofcrystallites of antimony-containing tin oxide in a unique associationwith amorphous silica or silica-containing material, metal coatedpowders, among others. In some cases, one or more components of the PECPcan comprise conventional ECP materials such as carbon, aluminum powder,among others. When incorporated into surface coatings, films and othersubstrates, PECPs impart electroconductivity while using a relativelylesser amount of antimony-containing tin oxide in comparison to theamount of antimony-containing tin oxide than would be required if theindividual component ECP types were used. In addition to providing asubstantial economic advantage, the PECPs reduce the quantity ofantimony that is present thereby minimizing color and achieving greatertransparency.

One unexpected result obtained by using PECPs is that the PECP is lesssensitive to the degree of loading, than when individual component ECPtypes are used thereby permitting enhanced control overelectroconductivity.

In one aspect of the invention the PECP composition may comprise atleast one filler particulate material, which is neither associated withantimony-containing tin oxide nor electroconductive, and at least oneECP.

In another aspect, the invention relates to a process for preparing thecompositions of the invention that consists essentially of a relativelygentle mixing procedure which is sufficient to cause an intimate mixingof the ECP components by intermingling individual component powderswithout significantly disrupting the electroconductive network coatingupon the component ECPs.

In yet another aspect, the invention relates to electroconductivecoatings which comprise or consist essentially of the PECP, whichimparts the conductivity, and a carrier matrix or vehicle system.Examples of suitable matrices or vehicles for producing anelectroconductive coating comprise at least one member from the group ofpaint, varnish, plastic films, fabrics and paper, among others.

While the individual ECP components of the PECP are known in this artmixtures having properties of the PECP were heretofore unknown. The PECPhas a lower electrical resistivity (or higher conductivity) than wouldbe predicted by the weighted average of the electrical resistivities forthe component ECP powders, among other desirable properties. By reducingthe quantity of antimony that is necessary for conductivity, the PECPsolves color and transparency problems associated with conventionalECPs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1--FIG. 1 shows weight effectiveness for a range of PECPcompositions comprising ECP-M and ECP-S.

FIG. 2--FIG. 2 shows the relationship between surface resistivity andfilm loading for PECP compositions comprising ECP-M and ECP-S and forthe ECP-M component alone.

FIG. 3--FIG. 3 shows the weight effectiveness of a range of PECPcompositions comprising ECP-M and ECP-T.

FIG. 4--FIG. 4 shows the relationship between surface resistivity andfilm loading of PECP compositions comprising ECP-M and ECP-T and of theECP-T component alone.

FIG. 5--FIG. 5 shows the relationship between surface resistivity andfilm loading for PECP compositions comprising ECP-M and TiO2 and for theECP-M component alone.

FIG. 6--FIG. 6 shows the relationship between surface resistivity andfilm loading for PECP compositions comprising ECP-M and SiO2.

DETAILED DESCRIPTION

The present invention relates broadly to a new class or type ofelectroconductive powders (ECP), designated as Polytype ECP (hereinafterreferred to as "PECP"), comprising or consisting essentially of intimatemixtures of several types of ECP powders. PECP mixtures possess a lowerelectrical resistivity, or a higher electroconductivity, than would beexpected from the weighted average of the component ECP powders. PECPare multi-component and may contain many different types of ECP. Binaryor ternary mixtures are normally preferred.

ECP components of the PECP can be selected from at least one member fromthe group consisting of crystallites of tin oxide containing antimony insolid solution, crystallites of antimony-containing tin oxide withuniformly distributed amorphous silica, and two dimensional networks ofcrystallites of antimony-containing tin oxide in a unique associationwith amorphous silica or silica-containing material, metal coatedpowders, among others. The PECPs can be employed as a substitute forconventional ECPs, e.g., to enhance cost-effectiveness or obtainimproved performance. When incorporated into surface coatings, films andother substrates, PECPs impart electroconductivity while using arelatively lesser amount of antimony-containing tin oxide in comparisonto the amount of antimony-containing tin oxide that would be required ifthe individual component ECP types were used. In addition to providing asubstantial economic advantage, the PECPs reduce the quantity ofantimony that is present thereby minimizing color and achieving greatertransparency.

In one aspect of the invention the PECP composition may comprise atleast one filler particulate material, which is neither associated withantimony-containing tin oxide nor electroconductive, and at least oneECP.

In another aspect, the invention relates to a process for preparing thecompositions of the invention that consists essentially of a relativelygentle mixing procedure which is sufficient to cause an intimate mixingof the ECP components by intermingling individual component powderswithout significantly disrupting the electroconductive network of thecomponent ECPs.

In yet another aspect, the invention relates to electroconductivecoatings which comprise or consist essentially of the PECP, whichimparts the conductivity, and a carrier matrix or vehicle system.Examples of suitable matrices or vehicles for producing anelectroconductive coating comprise at least one member from the group ofpaint, varnish, plastic films upon fabrics and paper, among others. Insome cases, the PECP may be a component within a filled plastic, e.g.,polyester, acrylics, polyethylene, polypropylene, polystyrene,nitrocellulose, nylon, among others.

While the certain individual ECP components of the PECP are known inthis art, mixtures having properties of the PECP were heretoforeunknown. For example, the PECP has a lower electrical resistivity (orhigher conductivity) than would be predicted by the weighted average ofthe electrical resistivities for the component ECP powders, among otherdesirable properties. By reducing the quantity of antimony that isnecessary for conductivity, the PECP solves color and transparencyproblems associated with conventional ECPs. Normally, the total quantityof antimony in a PECP ranges from about 0.5 to about 20% by weight.

Suitable components for preparation of PECPs can be selected from knownECP materials.

ECPs can comprise or consist essentially of tin oxide containing about0.5 to about 12.5 wt % of antimony in solid solution without a corematerial; hereinafter referred to as "ECP-XC". ECP-XC comprises orconsist essentially of at least one member from the group ofcrystallites of tin oxide containing antimony in a solid solution[SnO2(Sb)] wherein antimony is substituted for tin in the tin oxidecrystalline lattice, crystallites of antimony-containing tin oxide withuniformly distributed amorphous silica, and two-dimensional networks ofcrystallites of antimony-containing tin oxide in a unique associationwith amorphous silica and/or a silica containing material, among others.The powders can be prepared by any suitable method such as described inJ.P. 61,286-224; hereby incorporated by incorporated by reference, orobtained from commercial sources, such as Zelec®-ECP-3005-XC which isavailable from DuPont, Wilmington, Del., U.S.A.. ECP-XC normally is acompositionally homogeneous material and therefore, can be subjected toaggressive milling and mixing procedures. The average particle size ofmicronized powder usually ranges between about 0.1 and about 5 microns.

The ECP composition can be a powder comprising or consisting essentiallyof shaped particles such as at least one member from the group ofamorphous silica, inert core particles coated with amorphous silica,hollow amorphous silica shells, among others. Suitable core particlescomprise at least one member from the group of oxides of titanium,magnesium, calcium, barium, strontium, zinc, tin, nickel and iron;carbonates and sulfates of calcium, barium and strontium; mica,cordierite, anorthite and pyrophyllite, among others. The primaryfunction of the core material is providing a shaped particle upon whichthe amorphous silica substrate can be deposited. These types of powdersand methods for their preparation are described in greater detail inU.S. Pat. No. 5,024,826 and European Patent Application Publication No.0 359569 (corresponding to U.S. patent application Ser. No. 07/386,765),the disclosure of which have been incorporated by reference.

ECPs in which silica is coated upon core particles comprising orconsisting essentially of mica platelets have a conducting layer ofantimony-containing tin oxide, hereinafter referred to as "ECP-M". Theaverage particle size of this material typically ranges from about 0.1to about 20 microns wherein the individual coated platelet shapedparticles have an aspect ratio of diameter to thickness that typicallyranges between about 10 and about 100. Normally, the platelet thicknessis less than about 0.25 microns. The platy morphology of ECP-Mfacilitates the particles forming an interconnecting electroconductivenetwork within a thin film. These powders, when dispersed in suitablebinders, e.g., "HTV" VARNISH, are essentially transparent.

Powders comprising or consisting essentially of hollow shells ofamorphous silica having a surface coating layer of antimony-containingtin oxide; hereinafter referred to as "ECP-S". The average particle sizefor ECP-S is typically in the range of 0.5 to 15 microns and theparticle shape, determined by the shape of the core material which isremoved after depositing a coating of amorphous silica, can beirregularly equiaxed or acicular. Generally this type of ECP providesthe highest efficiency-in-use based on the loadings required in filmcoatings to achieve a desired level of electroconductivity.

Powders comprising or consisting essentially of a silica coated solidcore of titanium dioxide covered with an conductive coating ofantimony-containing tin oxide; hereinafter referred to as "ECP-T". Theaverage particle size of this material is typically in the range of 0.1to 20 microns and the particles are predominantly equiaxed. While anysuitable method can be used for preparing this powder, the methoddescribed in U.S. patent application Ser. No. 07/874,878, filed on Apr.28, 1992, hereby incorporated by reference, is particularly useful.

The ECP component powders can also comprise or consist essentially ofabout 0.5 to about 20 wt % amorphous SiO₂ substantially uniformlydistributed with about 80 to about 99.5 wt % of crystallites ofantimony-containing tin oxide, wherein the antimony component of the tinoxide ranges from between about 0.5 to about 12.5 wt %. While anysuitable method can be used for preparing this powder, the methoddescribed in U.S. patent application Ser. No. 07/905,980, previouslyincorporated by reference, is particularly useful.

Further, one or more components of the PECP can comprise conventionalECP materials such as carbon, aluminum powder, among others. In somecases, the ECP components powders comprise or consist of hollow shellsof silica having a surface coating layer comprising at least one metalselected from the group of Pd, Pt, Rh, Re, In, Au, Ag, Cu Ni, amongothers. These metal coated powders are described in greater detail inU.S. patent application Ser. No. 07/979,497, filed on Nov. 20, 1992; thesubject matter of which is hereby incorporated by reference.

Characteristics of certain suitable component ECP powders are summarizedin Table 1.

                  TABLE 1                                                         ______________________________________                                        ECP COMPONENTS                                                                SiO2 COATED CORES                                                                      "XC"   "M"       "S"       "T"                                       ______________________________________                                        Av. Part 1.                                                                              0.1-5    0.1-20    0.5-15  0.1-20                                  Size (microns)                                                                Aspect Ratio                                                                             -1       10-100    -1      -1                                      Tapped Density                                                                g/cc       0.3-0.7  0.4-0.7   0.2-0.6 0.9-1.3                                 Dry Powder                                                                    Resistivity                                                                   ohm-cm     -1       20-300     2-30    2-30                                   ______________________________________                                    

In another aspect of the invention one or more component powders can beparticulate material which is not associated with antimony-containingtin oxide and which is not electroconductive (hereinafter referred to asa "filler"), with the limitation that at least one type of ECP powdermust be a component of the PECP mixture. Powders suitable for use as afiller can comprise or consist of at least one member of amorphoussilica particles, hollow silica shells, the group of core particlesdescribed previously, among others..

The PECP compositions of the invention are intimate mixtures of theabove described components. By "intimate mixture" it is meant that theECP components are homogeneously mixed such that there are substantiallyno concentration gradients within the PECP. The mixtures may comprise orconsist essentially of binary, ternary, quaternary or multicomponentsystems depending upon the desired number of different ECP typesincluded in a mixture. For best results, an individual type of ECPtypically constitutes at least about 2 wt %, normally at least about 5wt % and usually at least about 10 wt % of the PECP. From a practicalstandpoint, ternary mixtures are normally preferred over multicomponentmixtures. Most preferred are binary mixtures with neither componentconstituting less than about 10 wt % of the mixture. When the content ofan ECP component is less than about 2 wt % its contribution to thesynergistic improvement in dry powder conductivity and end-useperformance tends to be reduced, if not eliminated. The proportions ofECP types which are mixed together to give a PECP depends on theparticular application for which the PECP is intended. Wide ranges ofadjustment can be made so that a PECP can be tailored with respect toboth the types of ECP and non ECP powders comprising the composition andto their proportions in order to achieve a desired combination ofproperties such as resistivity, transparency and degree of color orwhiteness.

PECP powders are prepared by an intensive but gentle mixing of thecomponent powders in which the individual components are intermingled toobtain an intimate mixture while minimizing any changes to themorphology and integrity of the individual particles. It is particularlyimportant in the case of ECP component particles having surface coatingsof antimony-containing tin oxide that the continuity of the coating notbe adversely affected, e.g., disrupted, by the mixing procedure. If themixing procedure is too severe these intermingling constraints are notmet and the electroconductive character of the ECP component particlesis adversely affected resulting in decreased performance in end-useapplications thus counteracting the desirable synergistic improvementobserved for PECP prepared by a suitable mixing procedure. On the otherhand if the mixing procedure is not sufficiently thorough the componentpowders are not intimately mixed and the resulting powder isinhomogeneous and very little improvement in performance is obtained,compared with the weighted average of the ECP components.

The "intermingling" of the component powders can be accomplished in anysuitable manner provided that the procedures comply with the aboverequirements. In some cases, the ECP component powders are passedseveral times, e.g., 10 times, through a commercially available samplesplitter and thereafter intermingled by using any suitable commerciallyavailable agitating or shaking equipment, e.g., a paint shaker for aperiod of at least about 30 minutes. While any suitable commerciallyavailable equipment such as a Patterson Kelly V-Blender can be used forintermingling the ECP component powders to obtain an intimate mixture,the following is an example of a suitable procedure which was used toprepare the PECP compositions described in the examples.

(a) Thoroughly blend the desired amounts of component powders, such asby passing the mixture at least 10 times through a commerciallyavailable sample splitter, or a sufficient number of passes to produce amixture having visual macroscopic homogeneity;

(b) Add the blended powders to a suitable container such as a jartogether with a mixing aid, such as small pieces of an elastomericmaterial;

(c) Agitate the mixture in the container by using, for example, acommercial paint shaker for a period of from about 10 to about 60minutes, normally about 30 minutes; and

(d) Separate the mixed powder from the mixing aid by using conventionalscreening or sieving methods.

Pieces of Tygon® polypropylene tubing, about 1" long and 1" in diameter,are suitable as a mixing aid when employed with an agitation means, suchas that produced by a commercial paint shaker is very effective inachieving the desired "intermingling" of the powders. A comparison ofdifferent mixing methods as a function of dry powder resistance (DPR)for a binary mixture consisting of 80 wt % of ECP-M and 20% wt % ofECP-S is listed in Table 2.

                  TABLE 2                                                         ______________________________________                                        EFFECT OF MIXING METHOD ON                                                    DRY POWDER RESISTIVITY OF                                                     80 WT % "ECP-M"(a)/20 WT % "ECP-S"(b)                                         D.P.R.(c)                                                                     4000 psi                                                                      MIXING METHOD                                                                              ohm-cm    REMARKS                                                ______________________________________                                        5 min, rolled in jar                                                                       118       Incomplete mixing                                      10 min, rolled in jar                                                                       97       Incomplete mixing                                      Intermingling(d)                                                                            86       Intimate mixing without                                                       damage to electro-                                                            conductive coating on                                                         particles (NITROGEN                                                           ABSORPTION) N2 Surface                                                        area = 33.4 m2/g                                       Ballmilled dry for                                                                         128       Significant damage to                                  60 min                 electroconductive                                                             coating on particles N2                                                       S.A. = 37.6 m2/g                                       Ballmilled dry for                                                                         153 × 10.sup.6                                                                    Severe damage to                                       96 hours               electroconductive                                                             coating and fracturing                                                        of particles                                                                  N2 S.A. = 48.1 m2/g                                    ______________________________________                                         (a)DPR = 286 ohmcm S.A. = 33.1 m2/g                                           (b)DPR = 8.9 ohmcm S.A. = 34.6 m2/g                                           (c)The D.P.R. values shown in Table 2 are averages of several                 measurements.                                                                 (d)Powders blended 10× through a sample splitter, mixed with pieces     of Tygon tubing and shaken for 30 minutes using a "Red Devil" Model 5410      paint shaker.                                                            

The effectiveness of the mixing procedure was ascertained by comparingthe dry powder resistivity (DPR) of the mixtures. The dry powderresistivity is an important property of the PECP compositions of theinvention. The electroconductivity of a powder is an inverse function ofthe resistivity and it is desirable that the dry powder resistivity beas low as possible so that the powder is most effective whenincorporated in coatings, films and other substrates to make themelectrically conducting.

Tumbling the powders for a period of about 5 to 10 minutes in a rotatingcylindrical container is normally inadequate to obtain an intimatemixture and the synergism between the components is not fully developedas is shown by the measured DPR values of Table 2. Ballmilling the mixedpowders for about 60 minutes is too severe and the electroconductiveparticle coatings are normally disrupted, e.g., the conducting networkof antimony-containing tin oxide crystallites is interrupted. Whenballmilling is continued for a longer period, such as 96 hours, theelectroconductive particle coatings are destroyed and fracturing ofparticles occurs, as evidenced by increased surface area. The DPR of themixture is higher by a factor of over one million showing that it isessentially non-conducting.

The dry powder resistance (DPR) was measured by using a cylindricalcell. The cell was constructed with brass electrodes at the top andbottom, that fit snugly inside a cylindrical piece of plastic having aninternal diameter of about 3 centimeters. Copper leads attached to thebrass electrodes were connected to an ohm meter. With the bottomelectrode in position a sample of powder was introduced into the plasticcylinder and the top electrode was placed in position above the powder.The height of the powder should be about 2.0 cm before applying pressureto the powder. Using a Carver laboratory press, the powder sample wascompressed at a pressure of about 4000 psi between the upper face of thebottom electrode and the lower face of the top electrode. The height andelectrical resistivity of the powder were then measured, the latter withthe ohm meter.

The value of the powder resistance, at the compression used, wasobtained, by the following calculation:

    Resistivity=(Resistance×Area)/Height;

"Resistance" is measured in ohms,

"Area" of cylinder cross-section in square centimeters, and;

"Height" is the length of the powder column between the top and bottomelectrodes in centimeters. In the case of the cell used in the followingexamples the area is 7.07 square centimeters. The PECP can be tailoredto obtain a virtually unlimited array of resistivities; normally fromabout 10 micro ohm cm to about 5,000 ohm cm. In most cases, the DPR ofthe PECP will be at least about 5% lower than the weighted Average DPRof the component ECPs.

The efficiency-in-use of a PECP for imparting electroconductiveproperties to a coating can be ascertained by dispersing the powder intoan aqueous vehicle containing a film forming binder such as an acrylicresin, e.g. "HTV" version The aqueous powder dispersion is coated onto aglass plate using a wet film applicator that can form an approximately0.003 inch thick wet film "drawdown" on the glass plate. After dryingfor about 14 hours, in air, the surface resistivity (S.R.) of thecoating is measured using a commercially available milli-to-2 ohmeter(Dr. Thiedig Corp) and a Model 803A surface/volume resistivity probe(Monroe Electronics Inc., Lyndonville, N.Y.). These instruments givedirect readings in ohms per square. The lower the value of S.R. thehigher the electroconductivity of the film. The surface loading ofpowder is determined by weighing the glass plate prior to and aftercoating, then multiplying the weight difference by the percentage ofpowder in the coating film and dividing by the area coated. The surfaceloading is conventionally expressed in pounds per 1000 square feet ofsurface, (lbs/Kft2). The drawn PECP containing films of the inventiontypically have a DPR that ranges from about 1×10³ to about 1×10¹²ohms/square.

The method that was used to determine the degree of transparency of theconductive coatings consists of preparing a conductive coating on an 1/8in. thick glass plate, i.e., a commercially available transparentwindow-glass. Then placing the coated glass-plate on a standardoptometrist eye-chart in direct contact with the eye-chart with thecoated side of the glass plate facing towards the observer and readingthe eye-chart from a distance of about 18 inches directly above thesample. The row number with the smallest print that can be read throughthe sample is the transparency number. The row with the largest print isrow #1 and the row with the smallest print size has the highest number.The better the transparency of the sample the smaller the print size andconsequently the higher the row number that can be read through thesample. A higher number corresponds to a higher degree of transparency.While the PECPs can be used in coatings having a wide range oftransparencies, the transparencies number that normally range from about2 to about 9. Such a transparency is at least about 3% greater than thetransparency that can be obtained by using the less transparent powdercomponent alone.

The method that was used for measuring whiteness/brightness correspondsto the procedure that is conventionally used with a Hunter Labscan ModelS.100 colorimeteric. It is a colorimetric measurement, known as theL*a*b* procedure, which utilizes a Hunter Labscan Model 5100colorimeter. This generates numerical values for L*, a* and b* whichdefine the whiteness/brightness (L*) and color (a*,b*) of the surfaceunder examination. L* relates to the degree of brightness or darkness ofthe sample with 100 being very bright and zero being very dark. Althoughthe PECPs can be tailored to possess a wide range of whiteness, usuallythe whiteness value L ranges from about 20 to about 95. Such a whitenessis at least about 2% greater than the whiteness that can be obtained bythe less white powder component alone.

The efficiency-in-use of PECP can be influenced in at least two aspects.The first aspect relates to the efficiency of the intra-networking ofthe antimony-containing tin oxide crystallites on the surface ofindividual ECP particles. The second aspect relates to the efficiencyrelating of the inter-networking between ECP particles. The latteraspect is caused by particle-to-particle contact which is a function ofparticle morphology and orientation. The intermingling of several typesof ECP powders, which may have different levels of [SnO2(Sb)], in thecomponent particles results in better than predicted properties, such aselectrical conductivity, transparency and degree of whiteness, comparedwith the weighted average of the individual types of ECP powder. Forexample in the case of ECP particles having mica platelet cores, i.e.,ECP-M, the particle aggregates may be in the form of "stacks ofplatelets" which is less efficient for coverage of a surface by aninter-network between particles. When such particles are intermingledwith the relatively equiaxed silica shell core ECP particles, i.e.,ECP-S, a surprising and unexpected effect can occur. Without wishing tobe bound by any theory or explanation it is believed that there is adestacking of the platelet-shaped ECP particles with the moreequi-dimensional silica shell core particles positioning themselvesbetween the platelets resulting in a configuration that covers an areaof surface more efficiently. In the case a mixture of generally equiaxedECP particles, e.g., a PECP of silica shell cores (ECP-S) and titaniumdioxide cores (ECP-T), it is believed that there is a declusteringeffect when the two types are intermingled. The declusteredconfiguration is substantially more efficient in covering a given areaof surface.

A range of PECP compositions comprising or consisting essentially ofmixtures of ECP-M and ECP-S between 100 wt % ECP-M and 100wt % ECP-S wasprepared by the "intermingling" procedure and evaluated in "HTV" varnishfilms in terms of surface resistivity. FIG. 1 is a plot of the weight ofPECP per unit area (lbs/1000ft2) required to obtain a surfaceresistivity of 10⁶ ohms per square in HTV draw-downs on glass. Plot "A"on FIG. 1 represents the measured surface resistivity of aPECP-containing film that was prepared from differing mixtures of ECP-Mand ECP-S. There was a surprising and an unexpected advantage in weighteffectiveness, and consequently cost effectiveness, for the optimum PECPcompositions in this system compared to Plot "B" of FIG. 1 which is theweighted average of the individual ECP components. The advantage of PECPover ECP alone is illustrated by the difference between Plot A and B,which is of the order of 20% to 30% over the composition range 10 wt %ECP-M/90 wt % ECP-S to 55 wt % ECP-M/45 wt % ECP-S. As a result, therelative effectiveness of the antimony-tin oxide component of the PECPin providing a given level of electrical surface conductivity issubstantially higher for a range of PECP compositions than for theindividual ECP components.

The degree of transparency of coatings containing PECP is considerablyhigher than those containing individual ECP components. Two typicalresults which illustrate this for coatings containing PECP consisting ofECP-M and ECP-S versus coatings containing ECP-S only are shown in Table3.

                  TABLE 3                                                         ______________________________________                                        RELATIVE TRANSPARENCY-POLYTYPE ECP                                            VS INDIVIDUAL ECP                                                                        COAT-    RELATIVE     SURFACE                                                 ING      TRANS-       RESISTIVITY                                  COMPOSITION                                                                              WT %     PARENCY      OHMS/                                        ECP        ECP      EYE-CHART(c) SQUARE                                       ______________________________________                                        POLYTYPE(a)                                                                              4        8, 8         2.5 × 10.sup.5                         INDIVID-   4        6, 6         4.5 × 10.sup.5                         UAL(b)                                                                        ______________________________________                                         (a)80 WT % ECPM/20 WT % ECPS                                                  (b)100 WT % ECPS                                                              (c)SCALE OF 1 to 9 (BEST)                                                

Another advantage of certain individual PECP compositions compared withthe individual ECP components is that, for any particular level ofelectroconductivity, coatings containing the former can havesubstantially higher whiteness/brightness values (L*). This is verydesirable in many applications particularly in ESD treatments forclothing and decorative materials. In the case of a PECP, in which thecomponents are ECP-M and ECP-XC, varnish coatings are applied to glassplates and L* values are measured.

The results are shown in Table 4 together with those obtained for ECP-XCevaluated in the same way.

                  TABLE 4                                                         ______________________________________                                        RELATIVE WHITENESS/BRIGHTNESS PECP                                            VS INDIVIDUAL ECP                                                                         COAT-                SURFACE                                                  ING      WHITENESS/  RESISTIVITY                                              WT %     BRIGHTNESS  OHMS/                                        COMPOSITION ECP      L*(c)       SQUARE                                       ______________________________________                                        POLYTYPE(a) 4        71; 69      7.0 × 10.sup.5                         POLYTYPE(a) 1        79; 79      1.2 × 10.sup.6                         INDIVID-    4        58; 56      6.5 × 10.sup.8                         UAL(b)                                                                        INDIVID-    1        75; 72      2.2 × 10.sup.9                         UAL(b)                                                                        ______________________________________                                         (a)90 WT % ECPM/10 WT % ECPXC                                                 (b)100 WT % ECPXC                                                             (c)L* = 100 FOR A PURE WHITE SURFACE                                     

The compositions of the invention have surprising benefits overconventionally used single component materials which are used to produceelectroconductive properties in non-conducting materials. For example,carbon black is widely used for this purpose but opacity and dark colorare often undesirable. White, transparent or lightly colored productswith surface resistivities in the 10³ to 10¹² ohms/square range areeasily achievable by using the PECP compositions of the invention. Alsoconductivity can be easily controlled and tailored for a desired rangeby using the PECPs of the invention.

The compositions of the invention are particularly useful in a varietyof applications such as an ingredient in electrically conductivecoatings, e.g., paints, varnishes, plastic coatings such asfluoropolymer coatings, among other coatings. The PECPs can also beincorporated into or applied onto conventional paper formulations forimparting dielectric properties, and fibers, films, foams, solidcontainers and packing materials for providing electrostatic discharge(ESD) resistance or protection.

While particular emphasis has been placed upon binary PECP mixtures, thePECPs of the invention can be multicomponent mixtures. By selecting theappropriate PECP components, the PECP can be tailored to possess avirtually unlimited array of characteristics, e.g., color, resistivity,transparency, cost effectiveness, among other characteristics.

The PECP compositions of the invention, methods of preparation andevaluation are demonstrated in the following examples for the purpose ofproviding more detailed information and illustrating the advantages ofthe present invention over the current state of the art. The followingExamples are provided for illustration purposes only and are not to beconstrued as limiting in any way the scope of the invention as definedby the appended claims.

EXAMPLE 1

This example describes preparing an PECP comprising differentproportions of mica core ECP (ECP-M) and hollow silica shell core ECP 9(ECP-S) powders, measurement of the dry powder resistivity (DPR) of themixtures and evaluation of electroconductive varnish films containingthe mixtures.

Approximately 170 grams of mica core ECP powder, (sold by the DuPontCompany under the trademark ZELEC® ECP-M) was weighed out and combinedwith about 30 grams of hollow silica shell core ECP (DuPont, ZELEC®ECP-S). ECP-M comprised about 4 wt. % antimony and had an averageparticle size distribution of about 8 microns, and ECP-S comprised about6.5 wt. % antimony and had an average particle size distribution ofabout 9 microns. The powder mixture was passed through a commerciallyavailable sample splitter, and mixed in a glass jar for about 30 minutesusing a paint shaker apparatus. To insure uniform mixing of the twopowder types several one-inch long pieces of plastic "Tygon" tubing wereadded to the powder in the glass jar. After the mixing was completed thepowder was separated from the pieces of "Tygon" tubing by screeningthrough a 20 mesh Standard Sieve. The dry powder resistivity wasmeasured by the procedure previously described.

A portion of the mixed powder was used as a solid filler in an aqueousbase paint dispersion of "HTV" varnish ("High Temperature Varnish"SS-10541 from Werneke-Long, Inc., Tinley Park, Ill.), in the followingconcentrations 1%, 2%, 3%, 4%, 5%, and 6% of PECP 85 wt % M/15 wt % S inthe aqueous HTV dispersion. So-Called "drawdowns" were made on glassplates using a wet film applicator giving an approximately 0.003 inchwet film thickness of the aqueous PECP/HTV resin suspension on the glassplates. After drying for about 14 hr. (overnight) the surfaceresistivity of the conductive coatings was measured as previouslydescribed.

Using substantially the same procedure several other "M"/"S" PECPcompositions, containing different proportions of "M" and "S" grade ECP,were prepared. The DPR and the surface resistivity of electroconductivevarnish coatings in which the compositions were incorporated weremeasured.

The DPR results are shown in Table 5 for the M/S binary series ofPECP's, including data for the individual ECP components. Thetheoretical DPR, the weighted average of the component DPR, iscalculated and is shown in Table 5. Using this and the actual DPRs thepercent synergistic improvement (SI%) is calculated using the formula:

                  TABLE 5                                                         ______________________________________                                        M/S PECP MIXTURES                                                             DRY POWDER RESISTIVITIES (DPR)                                                COMPOSITION DPR (OHM-CM)                                                      WT % M/WT % S                                                                             THEORETICAL   ACTUAL     SI %                                     ______________________________________                                        100M        286           286 average                                                                              --                                       85M/15S     244           114 average                                                                              53                                       80M/20S     231           86 average 63                                       70M/30S     203           63 average 69                                       50M/50S     148           35 average 76                                       15M/85S      51           15 average 71                                       100S         9             9 average --                                       ______________________________________                                         ##STR1##                                                                      M= ECPMICA CORE                                                               S= ECPSILICA SHELL CORE                                                  

The measured DPR were substantially lower than would be expected fromthe weighted average of the component DPR.

The surface resistivity results obtained on the electroconductivevarnish coatings are shown in Table 6. The results are expressed as ECPweight loading per 1000 sq ft to give 10⁶ ohms surface resistivity. In anumber of cases the average of several duplicate experiments for thesame composition is given.

                  TABLE 6                                                         ______________________________________                                        WEIGHT EFFECTIVENESS OF M/S PECP                                              FOR 10.sup.6 OHMS PER SQUARE SURFACE RESISTIVITY                              COMPOSITION    WEIGHT LOADING                                                 WT % M/WT % S  LBS/1000 SQ. FT.                                               ______________________________________                                        100M           0.59 average                                                   85M/15S        0.43 average                                                   70M/30S        0.50 average                                                   50M/50S        0.49 average                                                   15M/85S        0.69 average                                                   100S           0.66 average                                                   ______________________________________                                    

The data from Table 6 are plotted in FIG. 1. The graph shows that theweight effectiveness of certain PECP's in this system is substantiallysuperior to that of the pure components.

When surface resistivity is plotted against PECP weight loading in theECP-M/ECP-S system and compared with a similar plot for an individualcomponent of the PECP, the PECP weight loading curve has a relativelymore gradual slope in the low loading region. Referring now to FIG. 2,Plot "C" is represents the surface resistivity of ECP-M whereas Plot "D"represents the surface resistivity for a PECP consisting of 70 weight %ECP-M and 30% ECP-S. The gradual slope shown by Plot "D" illustrates thepractical utility of the PECP because such a slope means that surfaceresistivity is less sensitive to small changes in the ECP content of thefilm when PECP is used. This provides a substantial benefit in end-useprocessing because it facilitates obtaining a desired resistivity level.

Another unexpected and beneficial characteristic of PECP in the systemM/S is the fact that the relative conductive effectiveness (RCE) of thecontained antimony-tin oxide in providing a given level of electricalsurface conductivity is substantially higher for certain PECP mixturesthan for the individual ECP components alone. This is shown in Table 7,below.

                  TABLE 7                                                         ______________________________________                                        CONDUCTIVITY EFFECTIVENESS OF [SnO2(Sb)] IN M/S                               PECP FOR 10.sup.6 OHMS/SQUARE SURFACE RESISTIVITY                             COMPOSITION              CONTENT                                              WT % M/WT % S                                                                             WT. LOADG.   OF TOTAL                                             [SnO2(Sb)]  LB/1000 FT2  RCE1 (% NOMINAL)                                     ______________________________________                                                                 (A)       (B)                                        100M        0.59         39.1      0.043                                      85M/15S     0.43         42.5      0.055                                      70M/30S     0.50         45.7      0.044                                      50M/50S     0.49         50.3      0.040                                      15M/85S     0.69         58.2      0.025                                      100S        0.66         61.2      0.025                                      ______________________________________                                         ##STR2##                                                                 

EXAMPLE 2

This example describes the preparation of PECP comprising differentproportions of mica core ECP (ECP-M) and titanium dioxide core ECP(ECP-T), measurement of the DPC of the mixtures and evaluation ofelectroconductive varnish films.

Using substantially the same procedure described in Example 1 severalM/T PECP compositions, comprising different proportions of ECP-M andECP-T (sold by the DuPont Company as ZELEC® ECP-M and ZELEC® ECP-T)powders were used for preparing a PECP. ECP-T comprised about 4 wt. %antimony containing tin oxide upon a TiO₂ core particle, and had anaverage particle size distribution of about 5 microns. The DPR and thesurface resistivity of electroconductive varnish coatings in which thecompositions were incorporated, as described in Example 1, weremeasured.

The DPR results are shown in Table 8 for the M/T binary series of PECPincluding data for the individual ECP components.

                  TABLE 8                                                         ______________________________________                                        M/T PECP                                                                      DRY POWDER RESISTIVITIES (DPR)                                                PECP                                                                          MIX RATIO   DPR (OHM-CM)                                                      WT % M/WT % T                                                                             THEORETICAL  ACTUAL      S.I. %                                   ______________________________________                                        100M        286          286    average                                                                              --                                     67M/33T     193          36            81                                     50M/50T     145          28            81                                     33M/67T      96          11     average                                                                              89                                     100T         3           3      average                                                                              --                                     ______________________________________                                    

The measured DPR are substantially lower than would be expected from theweighted average of the component DPR.

The surface resistivity results obtained on the electroconductivevarnish coatings are shown in Table 9 wherein the results are expressedin ECP loading in pounds per 1000 sq. ft. to obtain 106 ohms surfaceresistivity. In a number of cases the average of several duplicateexperiments for the same composition is given.

                  TABLE 9                                                         ______________________________________                                        WEIGHT EFFECTIVENESS OF M/T PECP                                              FOR 10.sup.6 OHMS PER SQUARE SURFACE RESISTIVITY                              PECP                                                                          MIX RATIO                                                                     WT % M/Wt % TLBS/1000 SQ FT                                                                          WT LOADING                                             ______________________________________                                        100M                   0.69 average                                           67M/33T                0.68                                                   50M/50T                0.62                                                   33M/67T                0.60 average                                           100T                   0.83 average                                           ______________________________________                                    

The data from table 9 are plotted in FIG. 3. Plot "E" on FIG. 3 showsthat the weight effectiveness of certain PECP in this system wassuperior to that of the pure components that are represented by Plot"F".

The relatively gentle slope of the surface resistivity vs ECP loadingcurve for the PECP 67%T/33%M in the important region of low ECP loadingsis shown in FIG. 4. Referring now to FIG. 4, Plot "G" represents the100% ECP-T material that has a relatively steep slope in the region oflow ECP loadings in comparison to Plot "H" that represents a PECPconsisting of 67% ECP-T/33% ECP-M.

Another unexpected and beneficial characteristic of PECP in the systemM/T is the fact that the relative conductive effectiveness (RCE) of thecontained antimony-tin oxide in providing a given level of electricalsurface conductivity is relatively higher for certain PECP compositionsthan for the individual ECP components. This is shown in Table 10 below.

                  TABLE 10                                                        ______________________________________                                        CONDUCTIVITY EFFECTIVENESS OF                                                 [SnO2(Sb)] in M/T PECP FOR 10.sup.6                                           OHMS/SQUARE SURFACE RESISTIVITY                                                          CONTENT                                                                       OF TOTAL                                                           COMPOS-    WT. LOADING    [SnO2(Sb)]                                          ITION      LBS/1000 SQ FT (% NOMINAL)                                         % T/% M    (A)             (B)  RCE1                                          ______________________________________                                        100M       0.69   av.      40   0.036                                         67M/33T    0.68            40   0.037                                         50M/50T    0.62            40   0.040                                         33M/67T    0.60   av.      40   0.042                                         100T       0.83   av.      40   0.030                                         ______________________________________                                         ##STR3##                                                                 

EXAMPLE 3

This example describes the preparation of PECP comprising differentproportions of mica core ECP (ECP-M) and antimony-containing tin oxideECP without a core (ECP-XC) and measurement of the DPR of the mixtures.

Using substantially the same procedure described in Example 1 severalPECP compositions, comprising different proportions of ECP-M, ECP-XC(sold by the DuPont Company as ZELEC® ECP-M and DuPont, ZELEC®ECP-3005-XC) powders were prepared. ECP-XC comprised about 10 wt %antimony, lacked any core material, and had an average particle sizedistribution of about 2 microns. The DPR of the PECP compositions weremeasured and the results are shown in Table 11, including data for theindividual ECP components.

                  TABLE 11                                                        ______________________________________                                        PECP                                                                          MIX RATIO     DPR (OHM-CM)                                                    Wt % M/WT % XC                                                                              THEORETICAL  ACTUAL    S.I. %                                   ______________________________________                                        100M          286          286       --                                       95M/5XC       272          109       60                                       90M/10XC      257           83       68                                       50M/50XC      144           15       90                                       10M/90XC       30           2        93                                       100XC          1            1        --                                       ______________________________________                                    

The measured DPR are substantially lower than would be expected from theweighted average of the component DPR.

EXAMPLE 4

This example describes the preparation of PECP comprising differentproportions of mica core ECP (ECP-M), silica shell core ECP (ECP-S) andantimony-containing tin oxide and measurement of the DPR of themixtures.

Using substantially the same procedure described in Example 1 two PECPcompositions comprising different proportions of ECP-M, ECP-S and ECP-XC(sold by the DuPont Company as ZELEC® M, S and XC grade ECP powders)were prepared. The DPR of the PECP compositions was measured and theresults are shown in Table 12.

                  TABLE 12                                                        ______________________________________                                        PECP                                                                          MIX RATIO  DPR (OHM-CM)                                                       Wt % M/S/XC                                                                              THEORETICAL   ACTUAL     S.I. %                                    ______________________________________                                        75M/15S/10XC                                                                             216           54         75                                        15M/75S/10XC                                                                              50            8         84                                        ______________________________________                                    

The measured DPR are substantially lower than would be expected from theweighted average of the component DPR.

EXAMPLE 5

This example describes the preparation of PECP comprising mica core ECP(ECP-M), silica shell core ECP (ECP-S), titanium dioxide core ECP(ECP-T) and antimony-containing tin oxide and measurement of the DPR ofthe mixtures.

Using substantially the same procedure described in Example 1 a PECPcomposition comprising different proportions of ECP-M, ECP-S, and ECP-T(sold by the DuPont Company as ZELEC® M, S, T and XC grade ECP powders)was prepared. The DPR of the PECP composition was measured and theresult shown in Table 13

                  TABLE 13                                                        ______________________________________                                        PECP                                                                          MIX RATIO     DPR (OHM-CM)                                                    WT % M/S/T/XC THEORETICAL  ACTUAL    S.I. %                                   ______________________________________                                        132 30M/10S/50T/10XC                                                                        89           10        89                                       ______________________________________                                    

The measured DPR is substantially lower than would be expected from theweighted average of the component DPR.

EXAMPLE 6

This example describes the preparation of mixtures comprising mica coreECP (ECP-M) and certain fillers, namely, TiO2 powders and non-conductiveSiO2 shell powders. The DPR of the mixtures was measured and the surfaceresistivity versus ECP loading curve for varnish films containing themixtures was determined.

Using the procedure described in Example 1 the mixtures listed in Table14 were prepared. The DPR of the mixtures was measured and the resultsare shown in Table 14.

                  TABLE 14                                                        ______________________________________                                        PECP                                                                          MIX RATIO     DPR (OHM-CM)                                                    WT % M/WT % TiO.sub.2                                                                       THEORETICAL  ACTUAL    S.I. %                                   ______________________________________                                        100M           286            286    --                                       90M/10 TiO.sub.2                                                                            1257            148    88                                       70M/30 TiO.sub.2                                                                            3200            191    94                                       95M/5 SiO.sub.2                                                                              772            219    72                                       80M/20 SiO.sub.2                                                                            2229            481    78                                       100 TiO.sub.2 >10,000      >10,000   --                                       100 TiO.sub.2 "shells"                                                                      >10,000      >10,000   --                                       ______________________________________                                    

All the mixtures have a much lower DPR than expected which is anothermanifestation of unexpected synergism between the component powders.

Using the procedure described in Example 1 two of the mixed powders wereevaluated in an aqueous base paint dispersion of HTV varnish. Usingconcentrations of 1%, 2%, 3%, 4%, 5% and 6% of a) 70 wt % M/30 wt % TiO₂and b) 80 wt % M/20 wt % SiO2 "shells" in the aqueous HTV dispersion,glass plates were coated with films and the surface resistivity of thecoatings was measured as previously described. The measured surfaceresistivities are plotted against the percent ECP in the dispersion andthe results are shown in FIG. 5.

Referring now to FIG. 5, Plot "I" represents 100% ECP-M, whereas Plot"J" represents a PECP consisting of 70% ECP-M and 30% uncoated TiO₂.Referring now to FIG. 6, Plot "K" represents 100% ECP-M and Plot "L"represents a PECP consisting of 80% ECP-M and 20% uncoated silicashells. In each of FIGS. 5 and 6 data obtained illustrates that themixtures containing either TiO₂ or SiO₂ "shells" are found to have agentle slope whereas that corresponding to 100% ECP-M is relativelysteep in the region of low ECP loadings.

EXAMPLE 7

This Example describes preparing a PECP comprising ECP-M and a calciumcarbonate filler material.

Using substantially the same procedure described in Example 1 a PECP wasprepared from ECP-M and CaCO₃ (commercially available Calcium Carbonatesold as "HO-DRY"). The DPR was measured as described in Example 1. TheDPR results are shown in Table 15 for the ECP-M/calcium carbonate seriesof PECP including data for the individual PECP components.

                  TABLE 15                                                        ______________________________________                                        ECP-M/CALCIUM CARBONATE                                                       DRY POWDER RESISTIVITIES (DPR)                                                PECP MIX RATIO                                                                WT % M/WT %  DPR (OHM-CM)                                                     CaCO.sub.3   THEORETICAL  ACTUAL     S.I. %                                   ______________________________________                                        100M         286          286        --                                       98m/2 CaCo.sub.3                                                                           480          189        61                                       95M/5 CaCO.sub.3                                                                           743          209        72                                       90M/10 CaCO.sub.3                                                                          1257         215        83                                       100 CaCO.sub.3                                                                             >10,000      >10,000    --                                       ______________________________________                                    

EXAMPLE 8

This example describes the preparation of PECPs comprising differentproportions of ECP-S, ECP-T, and ECP-XC, and measurement of DPR.

Using substantially the same procedures described in Example 1 severalPECP compositions comprising ECP-S/ECP-T and ECP-XC were prepared. TheDPR was measured substantially as described in Example 1.

                  TABLE 16                                                        ______________________________________                                        Dry Powder Resistivities (DPR)                                                PECP MIX RATIO                                                                             DPR (OHM-CM)                                                     WT. %        THEORETICAL  ACTUAL     S.I. %                                   ______________________________________                                        100S         9            9          --                                       33S/67T      4.98         4.60        8                                       100T         3            3          --                                       67S/33XC     6.36         4.32       32                                       100XC        1            1          --                                       67T/33XC     2.34         1.57       33                                       ______________________________________                                    

EXAMPLE 9

This Example describes preparing a PECP using an ECP comprising silvercoated silica shells (hereinafter referred to as "Ag shells"). The Agshells were produced substantially in accordance with Example 3 of U.S.patent application Ser. No. 07/979,497, filed on November 20, 1992;hereby expressly incorporated by reference. The "Ag SHELLS" were madewithout tin (Sn) and without antimony (Sb).

Using substantially the same procedure described in Example 1, a PECPwas prepared from Ag shells, ECP-M, and uncoated mica. The uncoated micacorresponded to the particles that were used as core particles toprepare ECP-M. The DPR was measured as described in Example 1. The DPRresults are shown in Table 17 for Ag Shells/UNCOATED MICA and in Table18 Br Ag SHELLS/ECP-M including data for the individual components.

                  TABLE 17                                                        ______________________________________                                        Polytype ECP's Using Silver-Coated Shells                                     DRY POWDER RESISTIVITIES (DPR)                                                PECP MIX RATIO                                                                             DPR (OHM-CM)                                                     WT %         THEORETICAL  ACTUAL    S.I. %                                    ______________________________________                                        100% Ag Shells                                                                             0.6          0.6       --                                        80 Ag Shells/20 Mica                                                                          2000       0.89     99                                        100 Uncoated Mica                                                                          >10,000      >10,000   --                                        ______________________________________                                    

                  TABLE 18                                                        ______________________________________                                        PECP MIX RATIO                                                                              DPR (OHM-CM)                                                    WT %          THEORETICAL  ACTUAL    S.I. %                                   ______________________________________                                        100% Ag Shells                                                                              0.6          0.6       --                                       30 Ag Shells/70 ECP-M                                                                       200           77       62                                       100 ECP-M     286          286       --                                       ______________________________________                                    

While certain aspects have been described and illustrated above, aperson having ordinary skill in this art will recognize that allvariations and embodiments are encompassed by the appended claims.

The following is claimed:
 1. An electroconductive composition consistingessentially of an intimate mixture of at least two components wherein atleast one of the components consist of an electroconductive powder andanother component comprises at least one non-conductive filler whereinthe composition possesses a dry powder resistivity which is lower thanthe weighted average of said components.
 2. An electroconductive powdercomposition consisting essentially of an intimate mixture of at leasttwo components wherein one of said components comprisesantimony-containing tin oxide and another of said components comprises anon-conductive filler, wherein the composition possesses a dry powderresistivity which is lower than the weighted average of said components.3. An electroconductive powder composition comprising at least twocomponents wherein one of said components comprises a non-conductivefiller and said composition has an antimony content less than about 15%,a whiteness of more than about 20, and a lower dry powder resistivitythan the weighted average of said components.
 4. The composition ofclaims 1, 2 or 3 wherein said component is selected from the groupconsisting of crystallites of antimony-containing tin oxide, uniformlydistributed crystallites of antimony-containing tin oxide and silica,metal coated powders, and two-dimensional networks ofantimony-containing tin oxide crystallites upon at least one coreparticle; wherein said core particle is selected from the group of mica,titanium oxide, silica, and silica shells.
 5. The composition of claim 2or 3 wherein said filler is selected from the group consisting ofcalcium carbonate, silica, mica, silica shells, and titanium oxide. 6.The composition of claim 1, 2 or 3 wherein the transparency of saidcomposition is at least about 3% greater than the transparency values ofsaid components.
 7. The composition of claim 1, 2 or 3 wherein the drypowder resistivity is at least 5% lower than the weighted average drypowder resistivity of the components.
 8. The composition of claim 1 or 2wherein said composition consists essentially of a first component ofmica platelets having an antimony-containing tin oxide layer, a secondcomponent of amorphous silica having an antimony containing tin oxidelayer, and a third component of a non-conductive filler.
 9. Thecomposition of claim 1 or 2 wherein said composition consistsessentially of a first component of mica platelets having anantimony-containing tin oxide layer, a second component of titaniumdioxide having an antimony-containing tin oxide layer, and a thirdcomponent of a non-conductive filler.
 10. The composition of claim 3wherein said composition comprises a first component of mica plateletshaving an antimony-containing tin oxide layer, a second component ofamorphous silica having an antimony containing tin oxide layer, and athird component of a non-conductive filler.
 11. The composition of claim3 wherein said composition comprises a first component of mica plateletshaving an antimony-containing tin oxide layer, a second component oftitanium dioxide having an antimony-containing tin oxide layer, and athird component of a non-conductive filler.